The present invention relates to an ivory-like key material and a method for producing the same, and more particularly relates to production of artificial ivory-like key material of improved mechanical properties used for keyboard musical instruments such as pianos, organs and accordions.
Ivory has long been used for surface covering keyboard musical instruments because of its excellent inbred properties. With the increasing world trend for protection of wild animals, however, supply of natural ivory is now quite limited. As a substitute, use of artificial ivory-like material is widely accepted in production of keys for musical instruments. Casein resin made up of casein hardened with formalin is a typical example. In the case of such a casein-type artificial material, however, the texture of the product is rather poor when compared with natural ivory. In addition, the casein-type artificial material is rather vulnerable to impacts. Further, when a small amount of additives in the form of fine grains are contained in the casein, the material is poor in workability and breakage and cracks are often caused by cutting which is indispensable to production.
In an attempt to make the casein-type artificial material closer to natural ivory, it is proposed in Japanese Patent Opening Sho. No. 57-45592 to add a hydrate inorganic filler such as aluminium hydroxide to powdery casein before hardening by formalin. Inclusion of hydrate inorganic filler provides the product with moderate hygroscopicity to absorb sweat on the musical instrument player's fingers. The product also has comfortable smoothness with moderate abrasion resistance to provide excellent finger touch. Its deep translucent tint much improves the appearance.
Despite these advantages, addition of such an inorganic filler tends to develop contamination at the interfaces between casein and additives to lower the commercial value of the product.